1. Field of the Invention
The present invention relates to an automatic angle adjustment unit that automatically adjusts angles of a detection unit from the exterior, for an object detection device which receives, by section of a receiver, detection beams transmitted from a transmitter and detects for an object based on the reception level.
2. Description of Related Art
In general, a transmitter-receiver opposing type object detection device includes: a transmitter having a transmitting optical system (detection unit) for transmitting detection beams, such as infrared rays, for object detection; and a receiver that is disposed so as to oppose the transmitter and has a receiving optical system (detection unit) for receiving the detection beams and outputting a detection signal, and the object detection device of this type detects an object according to change of a detection signal level that is caused by an intervention between the two detection units, and has an angle adjustment mechanism for adjusting an optical axis (angle) of each detection unit. When the optical axis is adjusted, a vertical angle of each detection unit about a horizontal axis and a horizontal angle of each detection unit about a vertical axis are manually adjusted by visual observation with the use of a sighting device, thereby adjusting the optical axis.
On the other hand, an automatic angle adjustment device with an infrared sensor for automatically adjusting an optical axis has been known to date (see, for example, Japanese Laid-Open Patent Publication No. 2009-87240). In this angle adjustment mechanism, an optical axis of a transmitter is oscillated or swung by predetermined angles in two directions orthogonal to each other, and is set at an angular position obtained when a level of a signal received by a receiver is maximal. The optical axis is automatically oscillated by driving a motor in the device according to a signal level.
However, in Japanese Laid-Open Patent Publication No. 2009-87240, in order to automatically adjust the optical axis, an automatic angle adjustment section including: a driving motor for adjusting a vertical angle and a horizontal angle; and a control section thereof, is incorporated in the device, thereby increasing the size and cost of the entirety of the device.
On the other hand, a detection device and an automatic angle adjustment section may be separated from each other, and an optical axis may be automatically adjusted by an automatic angle adjustment unit from the exterior of the device. However, in a typical angle adjustment mechanism, a vertical rotation component for rotating the detection unit about a horizontal axis is incorporated so as to be mounted on a horizontal rotation component for rotating the detection unit about a vertical axis. Further, a horizontal adjustment component, like a dial, which is connected to the horizontal rotation component and drives the horizontal rotation component, and an adjustment component, like a screw, which is connected to the vertical rotation component and drives the vertical rotation component, are provided so as to be spaced from each other. When change of a position of the horizontal rotation component causes change of a position of the vertical rotation component, a position of the adjustment component is also changed. Therefore, there is a structural problem that the automatic angle adjustment unit cannot be easily attached to and detached from the device.